I cant figure my fuel pressure problem cant get it above 52 psi changed the pump.filter,regulator when key is turned on it jumps to 60 then immediately drops to 50 running its at 48-50 it jumps to 60 when I take the vacuum hose off regulator any suggestions

that's about right. key cycled to turn on the fuel pump, do not start the engine, (keep cycling until the max fuel pressure is reached) it should be 66-62 psi. Start engine the fuel pressure should drop 3-10 psi. that's normal operation.

are you having a problem? what is the problem? why have you change all those parts?

if your truck has fuel problems you should look at you fuel trims and check for codes.

giving me the code is helpful but it's only one step in trying to fix a problem. Is that all that you have for information? Can you feel the misfire? Is the engine running rough? Do you feel the engine jerk on accell? The more information I have the more I can understand what you are looking for.

When you ask about fuel pressure, that's what info I can give you. When you say you have a P0300, then that a little more information I can give you. But all that will just be general info. It may or may not help you at all.

you should hook up to a scanner that has misfire counter data. Then you can watch all the cylinders and see which ones are missing and how often. That will help you narrow down on what to address.

Also looking at the fuel trims. If you have low fuel pressure that's causing the problem the fuel trims will be high to compensate for lack of fuel.

you probably have a bunch of miles on a truck from 2002, have you ever cleaned the injectors? I have had many GM vehicles the seem to run fine. No rough running or anything but get the p0300 code. A good injector cleaner like Motorvac or even a gas additive that is made to clean injectors and the problem goes away.